Sienna Miller showed up at "The September Issue" New York City premiere yesterday looking slightly retro with round pink sunglasses and definitely sexy in a light blue mini dress. See more photos after the jump...

Image © Janet Mayer / PR Photos

"The September Issue" is a documentary which focuses on Vogue editor Anna Wintour as she visits the annual Fashion Week shows, accepts or dismisses the latest creations of the biggest names in fashion, works with the models, photographers, and writers who help bring her vision to the page, and labors with her staff to determine what the world's fashionistas will be wearing for the next 12 months.

Image © Janet Mayer / PR Photos

"The September Issue" received its world premiere at the 2009 Sundance Film Festival, where it received an award for excellence in documentary cinematography.